Brake mechanism



Nov. 17, 1953 Filed July 30, 194e E. G. MUELLER 2,659,456

BRAKE MECHANISM 4 Sheets-Sheet l 70 57 5.9 37 :1 I 51j. 26 l.l 1,1/ 56 M 56 41 ga *fl :1o. 5f

/U'J '72 Y INVENTOR.

Emil G.Muellel [75g 5. BY*

HIS 4T TORNEY Nov. 17, 1953 E. G. MUELLER BRAKE MECHANISM 4 Sheets-Sheet 2 Filed July 30, 1948 INVENToR. Emi-l G. Mueller HIS ATTIZNE'Y E. G. MUELLER BRAKE MECHANISM Nov. 17, 1953 4 Sheets-Sheet 3 Filed July 50, 1948 Nl Ee Vu WM Q m E HIS ATTRNEY E. G. MUELLER BRAKE MECHANISM Nov. 17, 1953 4 sheets-shea 4 Filed July 30. 1948 INVENTOR.

Emil G. Mueller H15 ATTORNEY Patented Nov. 17, 1953 BRAKE MECHANISM Emil G. Mueller, Churchill, Pa., assignor to The American Brake Company,

corporation of Missouri Application July 30, 1948, Serial No. 41,650

My invention relates to brake mechanism for railway trucks. It is described herein as applied to a truck for an electrically propelled locomotive adapted for operation in either direction. Certain features of my invention are of especial utility in connection with trucks adapted for operation in either direction. Certain other features are of especial utility in connection with trucks for electrically propelled locomotives. Still other features are of general utility in connection with railway trucks.

The phrase electrically propelled locomotive as used herein is intended to include any locomotive whose drive wheels are rotated by electric motors, regardless oi the source of the electrical energy supplied to the motors. Such locomotives commonly have the space between their drive wheels largely taken up by motors and driving gears, so that the space available for the brake mechanism is limited.

When a brake shoe is applied to a rotating wheel on a railway truck, the reactive and fricticnal forces on the shoe produce a moment tending to tip or rotate the truck about its lateral axis. This "truck tipping effect is one of the factors which limits the permissible braking force and hence must be considered when making a choice of a brake mechanism for a railway truck.

A railway truck adapted for normal operation in either direction must be provided with brakes which operate equally well in either direction. It is therefore usual to provide such a truck with a brake shoe arrangement which is symmetrical about the lateral axis of the truck. This limits the number of possible brake shoe arrangements which may be considered for such a truck.

It is an object of my invention to provide a brake mechanism in which the truck tipping effect is minimized.

Another object is to provide an improved brake mechanism :for a railway truck adapted to be operated in either direction.

further object of my invention is to provide an improved compact brake rigging of the unit cylinder type.

I accomplish these objects by providing a brake mechanism for a four-wheel truck including one shoe for each wheel on the side of the wheel farthest from the truck center and two shoes for each wheel on the side of the wheel nearest the truck center. It is demonstrated in connection with Figs. 1 and 2 that for any symmetrical arrangement of brake shoes, the moments of the shoes nearest the center of the truck act in oppo- 9 Claims. (Cl. 18S-56) Swissvale, Pa., a

sition to the moments of the shoes nearest the ends of the truck. Since the end shoes are farther from the truck center, their moment arms are greater and hence the tipping moments of the end shoes are greater per shoe. I overcome this predominance of the tipping moments of the end shoes by using two shoes on the center side of each wheel and only one shoe on the side of the wheels nearest the ends of the truck.

On a six-wheel truck, the brake shoe arrangement on the end Wheels is the same as on the four-wheel truck. The center Wheels of the sixwheel truck are likewise provided with two shoes on one side and one on the other, but the brake shoes are arranged oppositely on the center wheels on opposite sides of the truck.

My improved unit cylinder brake rigging includes a brake cylinder, an automatic slack adjuster, two transverse levers having their outer ends respectively connected to the piston rod of the cylinder and the automatic slack adjuster, two vertical levers having their upper ends respectively connectedto the inner ends of the transverse levers, a tie rod connecting the lower carried by the hangers. cylinder brake rigging are disclosed herein. These three species diiier as to the brake shoe and brakehead arrangements in each oase, and one species differs from the other two in the arrange ment of the transverse levers.

Other objects and characteristic features of my invention will become apparent as the description proceeds.

I shall describe several forms of brake mechanism embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is a A vector diagram illustrating the reactive and frictional forces applied to a railway truck during braking by a symmetrical arrangement of outer brake shoes. Fig. 2 is a similar vector diagram showing forces applied by a symmetrical arrangement of inner brake shoes. Fig. 3 is a side elevational View of a railway truck whose front wheel is provided with brake oording to one embodiment o1' my invention and whose rear wheel is provided with brake mechanism according to a modiiied form of my invention. Fig. 4 is a top plan view of the front wheel appearing in Fig. 3, with the brake mechanism applied thereto. Fig. 5 is a sectional view taken along the line V-V of Fig. 3, looking in the direction of the arrows. Figs. 6a and 6b taken together form a side elevational view of a six-wheel truck provided with brake mechanism in accordance with my invention. Fig. 7 is a side elevational view of the front wheel of a truck provided with a unit cylinder brake rigging according to another modified form of my invention. Fig. 8 is a top plan view of the wheel and brake rigging of Fig. '7. Fig. 9 is a View taken along the line IX--IX of Fig. '1. Fig. l is a view taken along the line X-X of Fig. 7. In several of the gures, certain parts are omitted for the sake of clarity.

Figs. 1 and 2 illustrate by means of vectors the reactive and frictional forces applied to a four-wheel truck during braking by symmetrical arrangements of inner and outer brake shoes. As used herein, the term inner brake shoe refers to a shoe acting on the side of a wheel nearest the center of the truck. The term outer brake shoe refers to a shoe acting on the side of a wheel farthest from the center of the truck. In the following discussion of Figs. 1 and 2, it will be demonstrated that the sum of the moments acting on the truck due to reactive and frictional forces applied through symmetrically arranged outer brake shoes is always in the same direction and is opposite to the sum of the moments due to similar forces applied through symmetrically arranged inner brake shoes.

Referring to Fig. 1, there is shown diagrammatically a railway truck I having front and rear wheels IA and IB spaced at equal distances from the truck center IC. The wheels IA and IB are provided with three sets of brake shoes. One set includes the shoes 2A and 2B, another includes the shoes 3A and 3B, and the third includes the shoes 4A and 4B. Each set is symmetrically arranged with respect to the truck center IC.

The principles involved in an analysis of the forces acting on one brake shoe are generally applicable to all the brake shoes. Therefore, I will first give a complete analysis of the forces acting on the brake shoe 2A, and will indicate how this analysis applies to the other `brake shoes by using similar reference characters to indicate the corresponding forces.

When the shoe 2A is applied to the Wheel, the wheel reacts against it with a force acting in a direction radially outward from the wheel center. This force is indicated by the vector 2AR in Fig. 1. Due to the rotation of the wheel, a frictional force ZAF is set up in a direction tangential to the wheel. The magnitude of the frictional force ZAF is dependent upon the magnitude of the radial force ZAR. and the coefficient of friction between the shoe 2A and the wheel IA. For the purposes of the present discussion, this coefficient of friction has been taken as 0.25. The length of vector 2AF is therefore illustrated as being 0.25 of the length of the vector' ZAR. The total force acting on the truck IA through the shoe 2A is the resultant of the vectors ZAR and ZAF. Adding these two vectors gives the vector ZAT representing the total force acting on the truck through the shoe 2A.

In order to determine the tipping moment about the center IC due to the force ZAT, it is convenient to resolve the vector ZAT into horizontal and vertical components. These components appear in the drawing as 2AH and ZAV, respectively.

The various force vectors for the several shoes are given reference characters consisting of the reference character of the shoe followed by the letter R for a radial reaction force, the letter F for a tangential friction force, the letter T for the total force, the letter H for the horizontal component, and the letter V for the vertical component.

Consider now the truck tipping moment caused by the forces acting on the truck through the symmetrically arranged shoes 2A and 2B. The horizontal forces ZAH and ZBH are nearly equal, and are opposite in direction. The resultant of these two opposed forces is therefore small. Furthermore, the moment arm of this small re- ,sultant force is short, since both forces act along a horizontal line only a short distance vertically above the truck center. It is therefore safe to ignore these horizontal components from the truck tipping standpoint. The vertical force ZAV produces a counterclockwise moment about the center IC. The vertical force ZBV produces a clockwise moment about the same center. Since the moment arms of these two forces are equal, and the force 2BV is greater than the force 2AV, it may be seen that the truck tipping' moment produced by the symmetrically arranged shoes 2A and 2B is in a clockwise direction about the truck center IC.

Considering the second symmetrical pair of shoes 3A and 3B, it may be seen that the radial reaction forces SAR and 3BR are horizontal and aligned with the truck center IC. The frictional forces SAF and BBF are vertical. Therefore the radial and friction forces are themselves the horizontal and vertical components, respectively, of the total forces SAT and BBT. Since the horizontal forces BAR and 3BR pass through the truck center IC, they produce no tipping moment about that center. The tipping moments due to the vertical forces SAF and BBF are both clockwise about the center IC, and the moment arm of both of these forces is substantially equal to the distance X appearing in the drawing. It may therefore be seen that the net truck tipping moment due to the symmetrically arranged shoes 3A and 3B is clockwise.

Referring now to the third set of shoes 4A and 4B, the horizontal component forces AAH and ABH may be neglected as far as truck tipping moments are concerned, since they are nearly equal and opposite and have a small moment arm. The vertical force ABV has a counterclockwise moment about the center IC, while the force 4AB has a clockwise moment. these two forces are equal, and the force AAV is larger than the force dBV. Therefore the net truck tipping moment due to the shoes 4A and 4B is in a clockwise direction.

From the foregoing discussion, it may be seen that for any symmetrical arrangement of the outer brake shoes with respect to the truck center IC, the net truck tipping moment is always clockwise if the direction of wheel rotation is assumed clockise.

In the foregoing discussion, it was tacitly assumed that all the reaction forces acting on the brake shoes are equal. Brake riggings are commonly designed so that the braking and reaction forces on each shoe are equal, so as to keep the wear equal on all the shoes. This assumption is therefore believed to be justified.

Referring to Fig. 2 there is shown a railway truck 5 having wheels 6A and 6B arranged at equal distances from the truck center 5C. These The moment arms of with three sets of brake shoes on their inner sides, arranged symmetrically with respect to the truck center 5C. One set of shoes is indicated at 1A and 1B, the second set at 3A and BB, and the third set at 9A and 9B. The various forces and force components acting on the brake shoes in Fig. 2 are indicated in the drawing using the same system of notation that was used in Fig. 1. Considering the tipping moment produced by the several sets of shoes, it may be seen that the shoes 'IA and 'IB produce a large counterclockwise moment due to the force l-AV and a small clockwise moment due tothe force iBV. Therefore, the net tipping moment due to this set of shoes is counterclockwise.

The shoes 8A and 3B produce two counter-clockwise moments due to the forces AF and SBF. The total tipping force due to these two shoes is accordingly counterclockwise, The shoes sA and 9B produce a small clockwise moment due to the force SAV and a larger counterclockwise moment due to the force SBV. The shoes SA and 9B therefore produce a net counterclockwise moment.

From this discussion of Fig. 2, it may be seen that any symmetrical arrangement or" shoes of the inner sides of the truck wheels produces a net counterclockwise moment, if the direction of wheel rotation is clockwise.

Although the spacing between the wheels is greater in Fig. 2 than in Fig. l, this is done for convenience in making the drawing only, and does not aiect the foregoing proof.

It has been shown that, assuming clockwise wheel rotation, any symmetrical arrangement or" outer shoes produces a clockwise moment, and that any symmetrical arrangement of inner shoes produces a counterclockwise moment. Therefore, in any symmetrical brake shoe arrangement including both inner and outer shoes the moments due to the inner shoes tend to counteract the tipping moments due to the outer shoes. However, since the outer shoes have longer moment arms than the inner shoes, the moments due to the outer shoes predominate. In the following braku ing arrangements, I minimize or completely eliminate the predominance of the tipping moments due to the outer shoes, by using two inner shoes and one outer shoe on each wheel, The greater number of inner shoes produces a greater wheels are provided tipping moment which compensates for the l greater moment arm oi" the opposing tipping moments oi the outer shoes.

While this method of minimizing truck 'tipping moments is always effective in brake riggings wherein the brake shoes are symmetrically arranged with respect to the truck axis, it may also be used in connection with unsymmetrical shoe arrangements. In such unsymmetrical arrangements, truck tipping may or may not be reduced by using more inner shoes than outer shoes, depending upon whether the tipping moment due to the outer shoes opposes that due to the inner shoes. If the tipping moments of the inner and outer shoes are opposed, then the net tipping moment may always be reduced by using a greater shoe area for the inner shoes.

Referring now to Fig. 3, there is shown one side of a four-wheel truck having a front wheel Ill and a rear wheel i I. rIhe front wheel I is braked by an outer shoe l2 and two inner shoes I3 and I4. The rear wheel l l is similarly braked by an outer shoe l and two inner shoes i8 and l?. Although the rigging which supports the two inner shoes I 3 and lil of front wheel l0 is illustrated as being diierent from the rigging which supports the inner shoes I6 and I1' of rear wheel II, it should be realized that on any actual truck, similar rigging arrangements would be used for all the wheels. The two diierent riggings are shown on one truck in the present drawings merely to avoid the necessity of repeating the illustration of the complete truck to illustrate each rigging.

The brake rigging which operates the three brake shoes I2, I3, and M of wheel Ill is illustrated in Figs. 3, 4, and 5. It includes a brake cylinder I8 which operates a piston rod I9. An automatic slack adjuster 20, of well-known construction, is attached to the end of cylinder I8 opposite the piston rod I9, and is also partially supported by a bracket ZI attached to the truck frame. One horizontally extending transverse lever 22 has its outer end pivotally attached to the end of piston rod I9. Another horizontally extending transverse lever 23 has its outer end pivotally attached to the automatic slack adjuster 29. Intermediate points on the horizontal transverse levers 22 and 23 are connected by a tie rod 24.

A pair of vertical levers 25 and 2S are positioned adjacent the opposite sides of the wheel It. The upper ends of the vertical levers 25 and 26 are connected to the inner ends of the transverse levers 22 and 23 by means of links 27 and 23, respectively.

The transverse lever 22 is supported by a pair of wear plates 2Q support 30.

The lower ends of the vertical levers 25 and 2e are connected by a pair of straddle rods 3|. The connection between straddle rod 3l and vertical lever 26 includes a manual slack adjuster 32, of any suitable construction.

A hanger lever 33 (see Fig, 3) is pivotally supported on the truck frame by means of pins, one of which is shown at 34, and is pivotally connected at its center to the vertical lever 25. brakehead 35 is pivotally attached to the lower end of hanger lever 33, and carries the outer brake shoe I2.

A hanger member 36 is pivoted by means 'of` pins 3'! to the truck frame. The lower end of hanger member 36 pivotally supports an equalizer lever 38. The equalizer lever the hanger member 36 near erally indicated at 4I, of known construction.

The brake shoes, brakeheads, and hanger levers are for the most part omitted from Fig. 4,

in order to more clearly illustrate the other parts transverse lever 22 to rotate counterclockwise, thereby moving tie rod 24 to the right, and moving link 2'! to the left. Two components of motion of the transverse lever 22 are simultaneously taking place. ponent is about the inner end of the lever as a fulcrum, and tends to move the tie rod 24 to the right. The other component is about the pivotal connection between lever 22 and tie rod 24 as a fulcrum, and tends to move the inner end of lever 22 and link 21 to the left.

The motion of tie rod 24 to the right is transcarried by a channel-shaped 38 is supported by its center, and its opposite arms in turn pivotally support brakeinittedithroughtransverse lever. 23, linkf28, andE vertical' lever 26;' tothe equalizer 38, andfthence to the brake shoes then the tierod 3iV may'act'uponfurther movement of the upper end of the'. opposite vertical lever'to transmita brake applying movement` to' the vertical lever whose upper endhas failedV to move.

Referring to the rear Wheeli I in Fig. 3, it'mayf bei seenzthat the. brake rigging for'the outer shoe l5v is acounterpartof the brake rigging forthe outer shoe |21 oftheront wheel l0. Theinner shoes I6 and IT, on the other. hand, are bothv supported onV a brakehead 42. which is pivotally attached to abrake hanger 2B which are the counterparts of the corresponding elements of thebrake rigging of front wheel Ill.l

The operation of thefrigging on the. rear wheel His similar to that' of'.V the rigging on the front wheel I0; and` further. description of it is' be` lieved to be unnecessary.

Thetwo innerrshoes on each wheel produce a truck tipping'torque which. opposes that of the outer shoes. Although the total braking force applied by'the inner'shoes is greater because of theirH greater-area (the rigging beingdesigned to produce equal brakingforces per unit area on all shoes), the moment. arm of' the truckV tipping force on the outer shoes isgreater, so that the two tippingmoments counterbalance each other. Tomakethis counterbalancing of. torques complete, the ratio of the areas ofthe inner and outer shoes should be substantially. the inverse ratio or the momentV arms' cfY the same shoes. For

example;.if the moment armof theouter shoesis twice that of the inner shoes, then theV inner shoesl should have anvv area twice that of the outer shoes. moment arms'andshoeV areas does not havelto berigidly followed. AlthoughA it representsthe ideal relationship; considerable variation fromA itl may beV allowed without undulyincreasing the .net tippingV torque.-

Figs'. Sai-6b' 'Ihese-iigures' areintended to be viewed' side' a six-wheel locomotive trucl: to which-s'appliedV albrake rigging similar to that applied to the four-wheeltrucl ofFigs. 3, 4, and`5. Figs. (ia-6b illustrate one side only of the truck, including' a front Wheel 43, a centerA wheel M',- and` a rear wheel 45. Thel front wheel Q55' is provided with a brake rigging which' is the same as that provldedifor the front wheelv truclcin Fig. 3; Thefrear wheel` 5 is provided with a brake rigging which is the sarneas that provided' for therear'wheel ilin Fig. 3l The centerwheel 44 is provided with a rigging-simiL lar-to that provided forfront wheel 0,3, except that it is reversedfrom left to right, so that? the Single shoe i2 appears. at the. left-hand sideof Wheel lillA and the two shoes.A i3 and I!! engage the. right-handr sidey of wheel 44;

The frontV andrear wheels ony the opposite side of the truolr: are, provided with brake. rige gings. Whichare enantiomorphic counterparts" of i3' and I4. MovementA of linka 2'1to the leftis transmitted through verticallevei 36 and a vertical lever Of course, .this relationship between.

itl' of the four-wheel the brake riggingsv applied to wheels :13'V and" 45 In other words, thev riggings for wheels are substantially balanced, so that the net truck tipping. moment due to the braking forcesV on thev center wheels. isV very small. It wouldbe possibleof course, to" use a symmetrical arrangement. of `brake shoes onbothoff theA center wheels, so thatV the truck. tipping moments onV the opposite sides of each wheelwould balance. However, the rigging for'suchr an arA rangement would have the rigging for the front and truck. By using the' arrangement shown, possible to use corresponding parts for the rig'- gings oi all six wheels. of the truck.

Figs. 7 i0 10 There is illustrated in Figs. 7 to 10 a modied form of br -ge rigging which maybe substituted for that shown on. the front wheel iii of Figs. 3, e, and 5. or on the reanwheelv li of Fig. 3.

In this rigging, aA brake cylinder 46 piston rod a transverse lever An. intermediate point on the Ytransverse lever is connectedftoa xed support by a linsr. The inner end of transverse lever @e is connected by a link to the upper end or" a vertical lever 5l..

rlhe lower end of lever. 5i is connected by straddle rods 52 and aslack adjuster. 52a tothe lower end of a vertical lever 53. The upper end lever 53 is connected by alink. 54 to. theinner l of another transverse lever 55. The outer end of lever 55 is supported by an. automatic slacl: adjuster 55 which is att'aclfiedltoV the cylinder dii and to a supporting bracket 51;

An' intermediate point on thetransverse lever through a bearing 6i in the truck frame. At thev inner end ofbearing 6i, the crankshaft 60 carries another crank arm. 52 which supportsat its lower end a braizehead 63 carrying. a. brake shoe 54.

y rline-angularposition of bralehe'ad 63 with respect to-crani; arm $2`is determined by a slipfriction' connection betweenA a brakehead pin. 53a.

(Figs. Tand-10) and a strap 62a which is oon.-

nected to crankshaft 63 for rotation therewith..

The strapa is used-because itis relatively light and flexible as compared to the crank arm 6.2,

is therefore more readily. adaptable to the.

formation of a slip-friction connection with pin E3c cy'tne use'of a spring washer on the pin.

braie hanger leverl G5 is' pivotally attached.

at its upper end to the' truck frame and at an intermediate point to the vertical lever 5S. At.

its lcv-.ier end, the han'ger'E5` carries a brakehead 6u which supports ak brake shoe 61.

-Both the shoesrfi and 6T engage the. innerV side' of a wheel B8.

A hanger lever e9 is pivoted at its upper endl on; theftruck frame and nearits center to the verticairlever 5I. At itsl lower end,- the hanger. lever 69 carriesla hrakelfi'eadi 'lwhich supports abraiie shoefiiinaposition to enga e the o side; ofz the? wheel. 68 g uter the front andrearwheels ofthe six-wheel truck are the same that. the riggings onI the oppocenter wheelsy in this' manner, the truck tippingrtorques of the' center" to be quitedifferent'froin. rear. wheels of the: it ist operatesi connected to the outer end of Operation of Figs. '.7v to 10 When the brakes are to be applied, air under pressure is admitted to cylinder s6, moving piston rod il to the right as viewed in Figs. 7 and 8. This moves the outer end of transverse lever @i3 to the right, causing it to rotate counterclockwise about its pivotal connection with link i9. The inner end of lever it is thereby moved to the left, moving link. ai? and the upper end of vertical iev/er 5i to the left.

This moves hanger lever te and brakehead 'iii to the left until brake shoe il engages wheel E8. Thereafter, the vertical lever 5i fulcrums about its connection with hanger S3, moving the lower end of lever 5 i to the right, carrying the straddle rods 52 in the same direction. The lower end of vertical lever 53 is thereby moved to the right, carrying the hanger 65 to the right and thereby moving brake shoe 6i into engagement with wheel t3. After brake shoe Si engages the Wheel, vertical lever 53 pivots counterclockwise about its connection with hanger t5, thereby moving the upper Yend of lever 53 to the left, and carrying link Se and the inner end of transverse lever 55 to the left. Lever 55 fulcrums about its outer end, carrying link 5S and crank arm 59 to the lef Crankshaft 60 is thereby rotated counterclockwise, carrying the crank arm 52 to the right to bring brake shoe 6s into engagement with wheel S8.

Although the brake shoes il, 6l, and S13 engage the wheel in that sequence, it should be appreciated that no appreciable braking force will be transmitted to any shoe until all three shoes are engaging the Wheel. This is because the rigging is arranged in the customary manner to require a reactive force at every shoe before any shoe can apply an appreciable braking force to the wheel.

From the foregoing, it should be apparent that in the several braking arrangements I have shown, the truck tipping moments due to the application of braking forces to the wheels are reduced to a minimum. Furthermore, since the brake shoes are arranged to be symmetrical with respect to the truck axis or effectively so, they may be used in trucks which are adapted for normal operation in either direction. Also, since substantially all or the brake rigging is mounted outboard of the truck wheels, the riggings are particularly well adapted for use with electrically propelled locomotives where the space between the wheels is largely taken up by the propulsion mechanism.

Although my invention is shown and described herein as applied to wheel brakes, wherein the shoes act directly on the running surface of the wheel, it may be readily applied to disk or drum type brakes, wherein the shoes act on the surface of a disk or drum which rotates concurrently with the wheel.

Although I have herein shown and described several forms of brake mechanism embodying my invention, it is understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described claim is:

1. Brake mechanism for a six-wheel vehicle truck comprising a braking surface on each wheel, three brake shoes for engaging each said surface, the three brake shoes for each end wheel of the truck being arranged with one shoe my invention, what I sitely, with two shoes on one side of each middle wheel and one on the other side, and means for simultaneously operating all said shoes into engagement with their braking surfaces.

2. Brake mechanism, comprising a rotatable element having a braking surface, a brake cylin.. der, a piston rod operated by said cylinder, a pair of transverse levers, a connection between the outer end of one lever and the piston rod, a pivot for the outer end of the other lever, a tie rod connecting` intermediate points on the two levers, a pair oi' vertical levers located at opposite sides or the element, a pair of links connecting the inner ends or the transverse levers to the upper ends ci the vertical levers, a second tie rod connecting the lower ends of the vertical levers, a pair of brake hangers located at opposite sides of the element, pivotal connections between said brake hangers and intermediate points on said vertical levers, an equalizer lever pivotally connected at its center to one hanger, a pair of brakeheads pivotally connected to the ends of the equalizer lever, a third brakehead pivotally connected to the other hanger, and a brake shoe on each of said brakeheads.

3. Brake mechanism for a vehicle wheel, comprising a brake cylinder, a piston rod operated by said cylinder, a pair of transverse levers, a connection between the outer end of one lever and the piston rod, a pivot for the outer end of the other lever, a tie rod connecting intermediate points on the two levers, a pair of vertical levers located at opposite sides of the wheel, a pair of links connecting the inner ends of the transverse levers to the upper ends of the vertical levers, a. second tie rod connecting the lower ends of the vertical levers, a pair of brake hangers located at opposite sides of the wheel, pivotal connections g between said brake hangers and intermediate points on said vertical levers, a pair of brakeheads each pivotally connected to one of said hangers, two brake shoes on one of said brakeheads, and a third brake shoe on the other brakehead.

4. Brake mechanism for a vehicle wheel, comprising a brake cylinder, a piston in said cylinder, a transverse lever having one end pivotally connected to the piston, a link connecting an intermediate point on the transverse lever to a fixed pivot, a pair of vertical levers located at opposite sides of the wheel, a link connecting the inner end of the transverse lever to the upper end of one of the vertical levers, a tie rod connecting the lower ends of the vertical levers, a pair of brake hangers at opposite sides of the wheel, a brakehead pivoted on each hanger, a brake shoe on each brakehead, a pivotal connection between each hanger and an intermediate point on the adjacent vertical lever, a second transverse lever having its outer end pivotally suported, a second link connecting the upper end of the other vertical lever to the inner end of the second transverse lever, a crank pivotally mounted and having two crank arms, a third link connecting the end of one arm to an intermediate point on the second transverse lever, a third brakehead pivoted on the end of the other crank arm, and a brake shoe on said third brakehead.

5. Brake mechanism for a vehicle wheel, comprising a brake cylinder, a piston rod operated by said cylinder, a pair of transverse levers, a connection between the outer end of one lever and semaine .thepiston rod, 1a pivot .for :the outer :end of .the .other lever, a tie .rod connecting intermediate lpoints .on Athe two levers, a pair of vertical levers located at. oppositesidesof .the wheel, a Lpair .of

vlinlisconnecting .theinner ends of the transverse leversto the upper ends ofthe Avertical levers,.,a lsecond tie .rod connecting ,thelowerends ,of the vertical leversa paiivof .brake hangerslocated atopposite sides of the wheelpiv otal Aconnections between said brake hangers and intermediate Ipointson said vertioallevers,l a brakeheadppivotally.n supported `by `each hanger,..and. at .least one brake shoe. on eachlbrakehead.

L6. Brake, mechanism lfor. a vehicle wheel,` comprising .a brake cylndena piston rodoperated jby.said.cylinder,.a pair of .transverse levers, a connection .between the `outer end .of one .lever and the ,piston ro'd, .apivotior the outer endof the other lever, a tie,rod.connecting.intermediate ,points on the two'leversapair.of vertical levers located at .opposite sides of the wheel, .means connecting ,the inner end of .each of the Ltransverseleversto the upper end of one o'f the 4vertical levers, arsecond ,tie rod connecting the `lowerendsof .the vertical' levers, a pair of..brake l .lhangerslocated atopposite sides vor Athe wheel, pivotal connections between ,said brake. hangers .and .intermediate points ,on .said vertical levers, a brakehead pivotally supported by each hanger, and at least .one brake shoe onea-ch .brakehead "7. ,Brake ,mechanism Afor. a vehicle Wheel,.. corn prising .abrake cylinder, va Ypiston rod. .operated hy said cylinder, a pairof transverse levers, a .coninectonbetween.theouterend of ,onellever and lthe piston rod,.automatic slack adjuster .means pivotallysupporting theouter end ,of the other lever, a tie rodconnecting intermediate points .on thetwo leversfapairof vertical levers located ,atopposite -sidesof the wheel,.means connecting the inner end Aor A eachof the `transverse 4levers to ,the upperendofone of .the vertical'levers, a second -tie .rodincludinga manual. slaolsadjuster ,connecting .thelovverends ofthe vertical levers, apair of brake hangers locatedatopposite sides of the wheel, pvotalconneotions between said brake hangers and .intermediate points onsaid vertical levers, a '.brakehea'd .,pivotally supported by each hanger, and atleast one brake shoeon each brakehead.

12 8. Brake-mechanism for a vehicle wheel, comprising a brake cylinder, a piston rod operated by said cylinder, apair of transverse levers, a

connection between the outer end of one lever andthe pistonrodgapivot forthe outer vend of the other lever, atie rod lconnecting intermediate points don the ltwo levers, Ya pair of vertical levers located at 'opposite sides `oi" the wheel, means connecting the inner end of each lof the transverse levers to-,the upper end of one of the vertical levers, a second tie rod connecting the lower ends of the'vertical levers, a pair of brake hangers located at opposite sides tof the wheel, 'pivotal Aconnections between said Ybrake hangers and intermediatepoints on'said vertical levers, twobrake'shoes supported on one of said hangers, `and one brake shoe supported on the other hanger.

`9. Bralre mechanism'for a vehicle wheel, comprising'a brake cylinder, a piston rod operated bysaid cylinder, a pair of transverse levers, a 4connection between the outer end of one lever andthe piston-roda pivot 'for the outer end of the other lever, fulcrum means pivotally convnectedto intermediate points on the two levers,

a pair of verticallevers located at opposite sides of the wheel, means connecting the inner end fof each of the transverse levers to the upper en'd of one of-the vertical'leversa tie rod connecting the lower ends of the vertical levers, a pair vof brake hangers located at opposite sides of the "-.wheeL lpivotal connections between the brake lhangers and intermediate points on the vertical levers, andatleast one'brake shoe supported on each hanger.

.EMIL G. MUELLER.

'vReferences'Cited inthe le of this 'patent UNITED STATES PATENTS YNumber AName Date :1,979,644 Saito Nov. 6, 1934 12,148,365 Baselt Feb. 21, 1939 2,169,751 Williamson Aug. 15, 1939 2,336,970 Tack Deo. 14, 1943 :2,343,939 lTack Mar. 14, 1944 A2,431,579 Mueller Nov. 25,1947 .2;446',659 `Mueller Aug. 10, 1948 

